The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos Hardcover – January 25, 2011

Excellent explanation of the competing theories surrounding parallel universes and their likelihood of existing. Delving into the outer limits of cosmology and theoretical physics, Greene always manages to remind us how little we actually know about reality and in so doing elicits the sense of awe inhering all around us.

Brian Greene's previous books are exemplars of what science writing should be: clear, wide-ranging in discussion and respectful of the intelligence of his audience. The Elegant Universe and The Fabric of the Cosmos are two of my three favorite popular science books. The third, Kip Thorne's Black Holes and Time Warps, is another superb example of science writing at its best. Now Brian Greene has added another masterpiece to the list. Everything that distinguishes Greene's writing style is in evidence in The Hidden Reality. His elegant prose is enjoyable to read. His brilliant ability to explain difficult abstract ideas in everyday language using easily understood examples still amazes me. And his use of vivid word pictures that always seem perfectly matched to the topic he's discussing propels his narrative forward so that the reader is never bored.

Yes The Hidden Reality is more accessible than his previous books. This book seems easier to read and is readily understandable. In his earlier books, I often read a paragraph several times in order to fully comprehend what Greene was attempting to communicate. That is something science and math majors are used to doing when reading textbooks but difficult for those not as scientifically adept. Greene's first two books dealt with Quantum Mechanics, String Theory and Einstein's Special and General Theories of Relativity: vast math-intensive topics that he was able to distill masterfully. The Hidden Reality inhabits a more abstract world, a conceptually challenging world. I quickly found Greene's more casual approach extremely helpful, even comforting, when I felt slightly adrift. The topics he discusses begin with the geometry of the universe: whether it is spherical (or positively curved), flat (with zero curvature) like a tabletop, or negatively curved like a Pringle.

The book devotes considerable time to the critical question of whether the universe is finite or infinite in size, something which has profound scientific and philosophical implications. It is a statistical certainty that in an infinite universe, regions of local space like ours will be endlessly repeated. In other words, assuming an infinite spatial universe with an expanding big-bang beginning, there are only a finite number of possible matter and energy configurations because the amount of energy and matter is finite. But there is an infinite amount of space within which those configurations will play out. Greene uses the example of a friend named Imelda whose passion for clothing has her purchasing 1000 pairs of shoes and 500 dresses. If Imelda is blessed with an infinitely long lifespan then, despite her vast wardrobe, if she changes outfits daily, within 1400 years she will have exhausted all possible new combinations. Imelda will be forced to repeat her sartorial choices. Philosophically, of course, all of that repetition of stars, planets and life's building blocks suggests that there are an infinite number of doppelgangers of each and every one of us. These infinite duplicates of ourselves would inhabit similar worlds that are forever hidden from mutual observation because the speed of light is finite. As Einstein showed in his Special Theory of Relativity, light-speed (300,000 km/sec) is the fastest rate by which information can be communicated. The bottom line: in an infinite universe the overwhelming bulk of reality remains hidden from its inhabitants by vast distances or by parallel dimensions harboring realities of every possible configuration.

In a finite spherical universe, on the other hand, the light from distant objects should ultimately traverse it several times, leading to multiple images of galaxies, for example. This hasn't been observed as yet, suggesting that the universe is either finite but huge or actually infinite in size. Though the size and shape of the universe remain undetermined, scientists when cornered tend to believe its size is infinite. Recent data also suggests that the universe is flat like a tabletop in shape.

Greene discusses all of the current hot topics in cosmology: brane-worlds, the multiverse, the holographic universe, unseen parallel worlds in dimensions separated by millimeters, our universe as a super-advanced computer program, the essentially hidden nature of reality. These are topics that have been discussed in other books but seldom with the passion for communication and clarity of thought that Greene exhibits in this one. The topics here are abstract concepts that exist at the very boundaries of human thought but Greene somehow manages to bring them down to earth. Even if you don't understand everything, the scientific vistas that Greene offers in this superb book are breathtaking in their intellectual beauty. You will find your personal horizons exponentially expanded. The Hidden Reality is replete with excellent illustrations that illuminate the material and are fun to look at. If this kind of science intrigues you then you will love this book. Brian Greene has written another masterpiece in a difficult genre.

This book is a fantastic follow-up to his previous book the Fabric of the Cosmos. In this book the reader is taken to a "hidden reality" of multiverses. Greene calls it a hidden reality because it reflects "the unique and uniquely powerful theme that underlies them all: the capacity of mathematics to reveal secreted truths about the workings of the world." And there are certainly a number of such multiverses - nine to be exact.

He starts with the quilted multiverse and continues with inflationary, brane, cyclic, landscape, quantum, holographic, simulated, and concludes with the ultimate multiverse. The first seven are rooted in where the mathematics of quantum mechanics, string theory, and relativity take us. If you examine the mathematics, it certainly allows for the existence of multiple universes.

An interesting concept that derives from living in a multiverse is that, as Greene notes, three primary aspects of our standard framework for the universe in which we live no longer are in need of explanation. They are no longer mysterious. They are: why the initial conditions were such as they were, why do the particles of the standard model have the values that they do or why do we have certain constants of nature, and why do we have the mathematical laws we do. You see, in a multiverse, this is all moot because the conditions that exist in our universe are just one set of conditions in one universe. There can be an infinite number of other universes where the mentioned parameters are somewhat similar or quite different. Some of them may even have your doppelganger.

I must make this comment about Green's writing. I have yet to read a book where someone can take an extremely complex subject matter (remember that these theories arise from some very serious mathematics), and render it understandable in concept by the non-mathematically inclined reader. I would say there were probably two sections in the book where I still was a little confused, but that is certainly my limitation. Greene has a real ability to use analogies to help clarify difficult concepts.

This is the third of book of Greene I have read, and I loved them all. I highly recommend this book if you have any interest in learning about the world we live in.

Very nice read for physics aficionados that are trying to understand the basics of String theory.

Greene's books usually try to explain things in a less-technical language, which is great for people interested in learning about such abstract concepts. Greene also takes his time to explain a little history behind the development of the ideas he introduces, so you get the context in which these theories were born.

I'm rating with four stars and not five, because sometimes his lexicon makes the read a little hard. And I'm not referring to technical or scientific language, but to unnecessarily sophisticated nouns, adjectives, verbs and gerunds. If english is not your home language, you might find yourself visiting the dictionary a little more than needed.

Nevertheless, I fully recommend this read to people interested in learning how close we stand today in understanding what reality is.

Didn't get bored until maybe halfway through chapter nine when the exposition turned to examining the examination. Still, I'm in awe and speechless. Bravo!

A lot harder, more complex and tedious than the other two books by Brian Greene. I just couldn't finish this one. Not for the layman.